As one of the industry non-destructive inspection apparatuses, X-ray photography systems are known. For example, an X-ray inspection apparatus having a micro-focus X-ray tube is used for inspection of electronic devices represented by semiconductor integrated circuit substrates. The X-ray tube is an X-ray source that applies a high voltage of a predetermined potential difference in accordance with X-ray energy between the anode and the cathode, irradiates a target with electrons accelerated by the high voltage, and thereby emits an X-ray from the target. The micro-focus X-ray tube is an X-ray tube having a plurality of grid electrodes on the cathode side and has a function of converging an orbit of an electron beam by controlling an electrostatic lens using a voltage applied to these grid electrodes.
In an X-ray generation apparatus using a micro-focus X-ray tube, a grounding scheme of the X-ray tube, a supply scheme of a control signal, and the like have been improved because of a need for controlling a voltage to be applied to grid electrodes. For example, the X-ray generation apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-317996 is configured to supply, via an optical fiber cable, a control signal of the grid voltage to be applied to the grid electrodes and thereby be able to apply a negative high voltage to the cathode of the X-ray tube. Further, an enclosure of the X-ray tube is defined as the ground potential, a neutral point grounding scheme that applies positive and negative high voltages to the anode and the cathode is employed, and thereby the voltage applied between the enclosure and the anode is reduced in about half.
In terms of easier handling or the like in mounting an X-ray generation apparatus on an X-ray photography system, reduction in size of the X-ray generation apparatus is demanded. Further, in terms of higher penetrating power, increase in a voltage applied to an X-ray tube is demanded. However, study by the inventors has revealed for the first time that malfunction in a control system increases due to progress of reduction in size and increase in application voltage of the X-ray generation apparatus.